1. Field of the Invention
The present invention relates to an angle switch device using a magnetoresistive effect (MR) element.
2. Description of the Related Art
U.S. Pat. No. 5,300,883, Japanese patent publication No. 08-005312A or Japanese patent publication No. 10-062112A discloses a sensor responding to a magnetic field applied from a magnet or a magnetic medium for example, for detecting a rotational angle. In each document, disclosed is an angle sensor with a Hall element that linearly detects a rotation-dependent magnetic flux density of the magnetic field applied thereto to provide an output representing the detected magnetic flux density.
In general, the magnetic flux density of the magnetic field from the magnet decreases proportional to a square of the distance from the magnet. Therefore, in order to linearly detect the magnetic flux density by using the Hall element, it is necessary to apply a magnetic field with a large magnetic flux density to the sensor element. Particularly, because the Hall element has a large temperature coefficient of about 10,000 ppm, required is a larger magnetic flux density to perform the rotational angle detection with stability. Therefore, the Hall element has to be used in conjugation with a magnet having a sufficiently large magnetic flux density or a magnet having a big volume.
Also, because the Hall element has the large temperature coefficient, when used to perform switching operation by comparing its output with a threshold so as to obtain a binary signal, it is quite difficult to expect precise switching operation even if the magnet is closely arranged with the Hall element.